1. Field of the Invention
The present invention relates to a manufacturing method of a magneto-resistance effect element preferably utilized for an MRAM (Magnetic Random Access Memory) which is an integrated magnetic memory, a thin film magnetic head, and the like.
2. Description of the Related Art
The MRAM is an integrated magnetic memory which has an integration density as high as a DRAM and a speed as high as an SRAM and also is a rewritable memory which can be rewritten without limitation, and thereby the MRAM is gathering attention. Further, the developments of a thin film magnetic head, a magnetic sensor, and the like are making respective rapid progresses using a magneto-resistance effect element such as a GMR (Giant Magneto-Resistance) element and a TMR (Tunneling Magneto-Resistance) element.
An example of the magneto-resistance effect element includes the one in which a lower electrode is formed on a substrate such as a silicon substrate, a glass substrate, or the like, and a multilayered film having eight layers constituting a magneto-resistance effect element (TMR) is formed thereon. An example of this multilayered film having eight layers includes the one in which a Ta layer serving as an underlayer formed in the undermost layer, a PtMn layer serving as an anti-ferromagnetic layer formed thereon, a magnetization pinned layer (pinned layer, Ru, and pinned layer), an insulating layer (barrier layer), a free layer, and a cap layer are stacked sequentially.
There has been a proposal in which a substrate having the multilayered magnetic film constituting the magneto-resistance effect element is processed by a thin film processing technique such as reactive ion etching (RIE) and ion beam etching (IBE) which have been developed in the semiconductor industry, to obtain a desired performance.
After the processing of the multilayered magnetic film has been completed, an insulating protective layer is formed thereon. Features required for this protective layer include a high break down voltage, a high step coverage, a small surface roughness Ra, and a uniform film thickness distribution even in a thin film (5 to 10 nm).
Conventionally, a method of using a sputter method or a method of using atomic layer deposition has been specified as a method of forming this protective layer (refer to Japanese Patent Application Laid-Open Publication No. 2003-59016 and Torii et al., TAIYO NISSAN Technical Report, No. 24 (2005) 2-7).
However, the conventional deposition method has the following problems.
(1) A high step coverage cannot be obtained in an Al2O3 protective film made by the sputter method.
(2) The Al2O3 film made by the sputter method is directly irradiated with plasma, and thereby a pinhole is formed in the insulating layer, which easily causes insulation breakdown.
(3) An Al2O3 film formed by using the atomic layer deposition (ALD) requires a long deposition time for forming an atomic layer.
(4) For the Al2O3 formed by using the atomic layer deposition (ALD), a complex chemical compound such as an alkylaluminum compound and aluminum alkoxide needs to be used as a source material (Japanese Patent Application Laid-Open Publication No. 2003-59016).
(5) The atomic layer deposition (ALD) uses a high temperature range of 150 to 350° C. (Torii et al., TAIYO NISSAN Technical Report, No. 24 (2005) 2-7).
(6) The Al2O3 formed by the atomic layer deposition (ALD) uses H2O as an oxidation agent and thereby a magnetic layer is damaged by water contained in the layer and a magnetic characteristic is degraded.